Add CancelChannelCreation() in protocol::Session interface.

remoting/protocol/pepper_session.cc

Index: remoting/protocol/pepper_session.cc
diff --git a/remoting/protocol/pepper_session.cc b/remoting/protocol/pepper_session.cc
index 373bfc3009df75270b767d07ede7b656e2d6bec3..ce56fd51432557c6e1cc472cffbb93f8477bee96 100644
--- a/remoting/protocol/pepper_session.cc
+++ b/remoting/protocol/pepper_session.cc
@@ -126,6 +126,14 @@ void PepperSession::CreateDatagramChannel(
   NOTREACHED();
 }
 
+void PepperSession::CancelChannelCreation(const std::string& name) {
+  ChannelsMap::iterator it = channels_.find(name);
+  if (it != channels_.end() && !it->second->is_connected()) {
+    delete it->second;
+    DCHECK(!channels_[name]);
+  }
+}
+
 net::Socket* PepperSession::control_channel() {
   DCHECK(CalledOnValidThread());
   return control_channel_socket_.get();